The robbery was reported at about 9:30 p.m. in the 700 block of Evelyn Court. The victim reported that several suspects in masks and dark clothing, two armed with guns, approached and demanded the keys to his home, according to the sheriff's office.
They took the man inside the home at gunpoint and ordered him to the floor as they went through various rooms. Someone then struck the man with a wooden chair and the suspects fled with property from the home, sheriff's officials said.
The home is in a quiet neighborhood where violent crime is rare.
"The fact that they just rolled up on the driveway is pretty scary. But we're in a safe neighborhood, you know?" said Spencer Jeha, who lives across the street.
The suspects and their vehicle remain at large. Anyone with information about the case is asked to contact the sheriff's Investigation Division at (925) 313-2600 or an anonymous tip line at (866) 846-3592 or email tipsso.cccounty.us.
Eric Thomas contributed to this report and will have more on this story starting at 5 p.m. on ABC7 News. You can follow him on Twitter here.